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Susceptibility-weighted imaging at high-performance 0.5 T magnetic resonance imaging system: Protocol considerations and experimental results

Published in Frontiers in Neuroscience, 1900

Abstract The high-performance low-field magnetic resonance imaging (MRI) system, equipped with modern hardware and contemporary imaging capabilities, has garnered interest within the MRI community in recent years. It has also been proven to have unique advantages over high-field MRI in both physical and cost aspects. However, for susceptibility weighted imaging (SWI), the low signal-to-noise ratio and the long echo time inherent at low field hinder the SWI from being applied to clinical applications. This work optimized the imaging protocol to select suitable parameters such as the values of time of echo (TE), repetition time (TR), and the flip angle (FA) of the RF pulse according to the signal simulations for low-field SWI. To improve the signal-to-noise ratio (SNR) performance, averaging multi-echo magnitude images and BM4D phase denoising were proposed. A comparison of the SWI in 0.5T and 1.5T was carried out, demonstrating the capability to identify magnetic susceptibility differences between variable tissues, especially, the blood veins. This would open the possibility to extend SWI applications in the high-performance low field MRI.

Recommended citation: Qiu, Y., Bai, H., Chen, H., et al. (2022). "Susceptibility-weighted imaging at high-performance 0.5 T magnetic resonance imaging system: Protocol considerations and experimental results." Frontiers in Neuroscience, 16, 999240. doi: 10.3389/fnins.2022.999240
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Spatiotemporal encoding MRI in a portable low-field system
The 2025 Young Investigator Award Winner

Published in Magnetic Resonance in Medicine, 2024

Abstract Purpose Demonstrate the potential of spatiotemporal encoding (SPEN) MRI to deliver largely undistorted 2D, 3D, and diffusion weighted images on a 110 mT portable system.

Recommended citation: Qiu, Y., Dai, K., Zhong, S., Chen, S., Wang, C., Chen, H., Frydman, L., & Zhang, Z. (2024). "Spatiotemporal encoding MRI in a portable low-field system." Magnetic Resonance in Medicine. 92(3), 1011-1021. doi: 10.1002/mrm.30104
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A new approach for multislice spatiotemporal encoding MRI in a portable low‐field system

Published in Magnetic Resonance in Medicine, 2024

Abstract Purpose Spatiotemporal encoding (SPEN) MRI offers a unique alternative to address image distortion problems in echo planar acquisition-based techniques, at portable low-field systems that lack multiple receiver coils. However, existing 2-π multislice SPEN schemes fail to keep consistent SNRs and contrasts with different numbers of slice settings. This work proposes a new multislice SPEN scheme (SPENms) to achieve stable quality imaging in portable low-field MRI systems.

Recommended citation: Qiu, Y., Chen, S., Solomon, E., et al. (2025). "A new approach for multislice spatiotemporal encoding MRI in a portable low‐field system." Magnetic Resonance in Medicine. 93(2), 709-717. doi: 10.1002/mrm.30300
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Multiband Fast Spin Echo on portable low-field systems

Published in Magnetic Resonance in Medicine, 2025

Abstract Purpose To improve the SNR efficiency of Fast Spin Echo (FSE) using RF-encoded multiband imaging and to develop techniques that correct artifacts from non-Carr–Purcell–Meiboom–Gill (CPMG) magnetization arising from system imperfections.

Recommended citation: Lee, P. K., Qiu, Y., Wang, C., & Zhang, Z. (2025). "Multiband Fast Spin Echo on portable low-field systems." Magnetic Resonance in Medicine. 1-16. doi: 10.1002/mrm.70036
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A Fast and Reliable Eddy Current Measurement Method in Portable Low-Field MRI

Published in IEEE Transactions on Instrumentation and Measurement, 2026

Abstract Portable permanent low-field magnetic resonance imaging (MRI) is gaining increasing attention due to its low-cost, safer scanning, and broad range of applications, such as emergency. However, frequent relocation of portable systems may alter their eddy current performances, which can degrade image quality unless timely recalibration is performed. The conventional eddy current measurement method relies on image-phase analysis and typically requires several hours in low-field MRI due to low signal-to-noise ratios (SNRs). In this work, a fast eddy current measurement method using field probes, which consists of an array of six 1H probes, is presented. The acquisition time was reduced by a factor of 100, from 9 h to 5 min while successfully reducing residual eddy currents to within ±0.03% of the applied gradient amplitude over the whole measurement. To overcome the poor SNR, the probe size was increased by leveraging the reduced susceptibility effects in low fields. Measurement sequences were optimized to address challenges such as field inhomogeneity and residual magnetism effects in low fields. Gradient preemphasis parameters were adjusted according to the derived eddy current parameters. To evaluate correction efficiency, phantom and volunteer experiments were conducted by acquiring eddy current maps, fast-spin-echo, and diffusion-weighted echo-planar imaging (DWI-EPI) images. It was found that corrections obtained using the field probe method outperformed those obtained by the image-phase-based method within the same measurement iterations, providing a more stable reduction of eddy current-induced artifacts. These results demonstrate the potential of the proposed method as a reliable, timely solution for eddy current correction in portable permanent low-field MRI.

Recommended citation: Chen, S., Qiu, Y., Zhong, S., Lee, P. K., Chen, H., & Zhang, Z. (2026). "A Fast and Reliable Eddy Current Measurement Method in Portable Low-Field MRI." IEEE Transactions on Instrumentation and Measurement, 75. doi: 10.1109/TIM.2026.3657556
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Diffusion Weighted Fast Spin Echo With RF-Encoded Slabs for Portable Low-Field MRI Systems

Published in Magnetic Resonance in Medicine, 2026

Abstract Purpose To develop a robust diffusion weighted (DW) acquisition with clinically feasible scan times for portable MRI systems.

Recommended citation: Lee, P. K., Qiu, Y., Chen, S., et al. (2026). "Diffusion Weighted Fast Spin Echo With RF-Encoded Slabs for Portable Low-Field MRI Systems." Magnetic Resonance in Medicine, 95(6), 3253-3269. doi: 10.1002/mrm.70292
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Multi-Shot Multi-Echo xSPEN Technique for Portable Low-Field MRI Systems

Published in NMR in Biomedicine, 2026

Abstract Purpose To develop and evaluate a Multi-Shot Multi-Echo cross-term Spatiotemporal Encoding (MS-ME xSPEN) sequence for highly compact, portable low-field MRI systems, improving imaging performance while preserving robustness to severe field inhomogeneity.

Recommended citation: Qiu, Y., Lee, P. K., Dai, K., Chen, S., Yang, S., Wang, C., Bai, H., Dang, Z., & Zhang, Z. (2026). "Multi-Shot Multi-Echo xSPEN Technique for Portable Low-Field MRI Systems." NMR in Biomedicine. doi: 10.1002/nbm.70294
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